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Path: utzoo!linus!philabs!cmcl2!rocky2!datagen!mrm
From: mrm@datagen.UUCP
Newsgroups: net.lang
Subject: Re: I/O operations in programming languages
Message-ID: <16@datagen.UUCP>
Date: Wed, 31-Aug-83 09:43:15 EDT
Article-I.D.: datagen.16
Posted: Wed Aug 31 09:43:15 1983
Date-Received: Thu, 1-Sep-83 21:30:56 EDT
References: <666@mit-eddie.UUCP>, <110@csd1.UUCP>, <1796@allegra.UUCP>
Organization: Data General Dist. Systems, Westborough, MA
Lines: 42

C does not have I/O built into the language per-se, since the compiler
proper does not recognize calls to printf et. all.  Rather it interprets
them as normal function calls (and/or macro replacements).  The user is
free to write his/her own `printf' that does input instead of output or
what have you.  Also C stdio is not completely portable since a header
file could change a declaration from `int' to `long' on any given machine
and the format strings must be changed manually from "%d" to "%ld".  On a
16 bit machine this would produce incorrect results, whereas on a 32 bit
machine it would produce correct results.  Since the I/O is not builtin,
the compiler cannot tell the I/O system the type of the variables through
dope vectors, and the poor user is left to manage as best s/he can.  This
discussion also brings to mind that this is a good case for bringing back
the old "%r" format.

For those of you who don't know, %r interpretted the next argument as a
nested format, thus you could make one macro be the standard format for
any given type, which you might print out in several different places.  For
example:

	#ifdef	PDP11

	typedef	long	type;
	#define	FORMAT	"%ld"

	#endif

	#ifdef	VAX

	typedef	int	type;
	#define	FORMAT	"%d"

	#endif


	type a;

	...

	printf( "a is %r\n", FORMAT, a );

(allegra,ittvax)!datagen!mrm